Ongoing surveys best way to detect dengue-carrying mosquito
Back in 2001, several East Maui residents started reporting fever, body aches and rashes.
One of them had just traveled in French Polynesia during a dengue fever outbreak. The state Department of Health eventually confirmed 20 cases of dengue fever in East Maui, and a crew hired with funds allocated for environmental emergencies went to work removing mosquito breeding areas. What made this outbreak interesting was that it was spread by the tiger mosquito, Aedes albopictus, common in Hawaii.
“We may be the only place in the world to confirm (that) dengue could be spread by the albopictus mosquito. It’s not an efficient carrier of the disease,” said Gary Gill, deputy director of the Health Department’s Environmental Health Administration. “In places where dengue is endemic, it is the aegypti mosquito that is the carrier.”
The invasive mosquito, Aedes aegypti, is famous for spreading dengue. Neither the mosquito nor dengue is widespread in Hawaii. Both periodically appear, but luckily not at the same time. Though conditions for the disease are prime in Hawaii because it is a global hub for tourism and commerce, dengue outbreaks are rare and typically occur when someone travels to an infested area, returns to Hawaii and is bitten by a mosquito, as happened in 2001.
According to Gill, immediate family members and neighbors are at risk, but the common tiger mosquitoes rarely eat from more than one source. The female mosquito finds a person (or animal), and, given the chance, feeds until her belly is about to burst.
In contrast, Aedes aegypti flit from person to person, taking a blood meal from multiple people and spreading any disease carried by the bloodsuckers. Aedes aegypti is not normally found on Oahu. “We have not, up until last year, identified any aegypti since the 1940s,” Gill said.
In January of 2012, a Health Department entomologist collected a trap containing what was later identified as Aedes aegypti at the Honolulu International Airport.
“We’ve found aegypti five times in the last year. Every indication is that this mosquito is either living and breeding at the airport, or it is regularly being reintroduced,” Gill said.
Mosquitoes can survive in the cabin, cargo hold or underbelly of an airplane coming from an infested area. Aedes aegypti are originally from Africa but have spread to tropical and sub-tropical regions of the world including Mexico, Asia and Australia.
From a public health standpoint, having a thriving population of dengue-spreading mosquitoes at the airport is a worst-case scenario, according to Gill.
“A person carrying the virus walks through the airport, and then it spreads to any number of people at the airport who will then take it to wherever they are going,” he said. “A single population of aegypti could easily spread dengue throughout the state. A dengue-carrier mosquito would be a concern for people who come here as much as for people who live here.”
If Aedes aegypti became established throughout Hawaii, it would set the stage for a consistent presence of dengue, like does in parts of Central and South America, India, Southeast Asia and Africa.
Ongoing surveys for mosquitoes are the best way to ensure early detection of this species. The Health Department continues to monitor mosquitoes at Honolulu International Airport, but surveys are limited to that airport and don’t include surrounding areas. Funding cuts in 2009 gutted the Department of Health.
At one point, 40 people worked on Oahu on environmental health but now only seven positions remain. Staff cuts throughout the state have left no capacity for mosquito monitoring elsewhere. “What’s at Kahului? We have no idea,” Gill said.
The Health Department is working with the state’s departments of Agriculture and Transportation to explore options for mosquito surveys at airports and harbors statewide. They are working to reduce mosquito habitat at the airport, removing bromeliads and dark undergrowth and replacing it with less mosquito-friendly landscaping.
Gill encourages homeowners to do the same, along with removing or changing water in outside open containers every week. For now it’s our best hope. Unless and until capacity is restored at the Department of Health, early detection of this devastating mosquito is up to the public.
* Lissa Fox Strohecker is the public relations and education specialist for the Maui Invasive Species Committee. She holds a biological sciences degree from Montana State University. Kia’i Moku, “Guarding the Island,” is prepared by the Maui Invasive Species Committee to provide information on protecting the island from invasive plants and animals that can threaten the island’s environment, economy and quality of life.